In the context of plastic container production, in particular the production of plastic bottles, the use of blow-moulding machines is known.
A blow-moulding machine comprises a plurality of moulding units or apparatuses for moulding the containers.
Generally speaking, a moulding unit comprises:                a mould having at least one moulding cavity;        a base mounted over the mould, forming at least one passage connected to a high-pressure fluid source;        a blow nozzle forming at least one conduit and connected to a bottom face of the base to be positioned between the base and the mould in such a way that the conduit is in fluid communication with the passage to receive the high-pressure fluid and convey it into the moulding cavity;        fastening means for coupling and uncoupling the blow nozzle to and from the base.        
In this context, there is a need to use the machine to make containers of different types and sizes.
Adapting the moulding unit (or the blow-moulding machine) to the production of containers of different sizes is known as changeover.
Changeover involves substituting the mould with another one having a different number of moulding cavities and substituting the blow nozzle with another nozzle having a corresponding number of conduits.
That means uncoupling all the blow nozzles and fitting other nozzles.
In prior art systems, this is a time-consuming and difficult procedure. The nozzles are fastened with a large number of screws and bolts which must be screwed off to remove the nozzles and then on again to fit the nozzles suitable for the required size.
This creates considerable inconvenience and raises machine operating costs.